On Thursday 11 September 2008 01:33:25 Robert Klemme wrote:
> On 11.09.2008 06:48, David Masover wrote:
> > The problem is, how do I detect a blocked thread, and execute some code
when
> > that happens?
>
> Block on what? IO?
Mostly, yes, but really any blocking operation. Could be a mutex. Could be a
sleep call. Could be it was deliberately suspended.
In other words, anything that would cause Thread#stop? to return true.
> In that case you probably want to use more threads
> as Ruby does handle this nicely.
Maybe not as nicely as I'd like, though -- I imagine 1.9's OS threads are
heavier. And it presents problems with garbage-collection, with my current
design.
> > The best I can think of is to poll, checking for #stop?, but that's
hackish,
> > and performance would be awful. Poll too often, and I burn CPU -- not
often
> > enough, and I end up with large windows of my app waiting for the poll
thread
> > to wake up.
>
> I do not have a clear idea of your app
It's an actor library, which means apps will be written for it.
(Maybe. I might still drop it and just use Dramatis.)
> but usually with multiple threads
> you use some form of synchronization (blocking queues, condition
> variables etc.).
Right. An actor library is designed to abstract all of that away.
Let me phrase it differently -- it's like having a hundred thousand fibers
that I want to execute at least once. I don't need to spawn a hundred
thousand threads -- and I can't, I remember the limit being around three
thousand in 1.9, and I really only need one or two.
But if one of those fibers blocks somewhere, I want to spawn another thread.
Ideally, I need N + S threads, where N is the number of CPUs my program can
use concurrently, and S is the number of other threads which are stopped.
That's oversimplifying a bit -- but if you want to know more, read about
Erlang's process model. I'm trying to do something like that. The technical
term for that is the "actor model".